The invention relates, in general, to barrier operators and, in particular to a garage door operator including a system for detecting when an attempt is made to force open a closed garage door.
Several garage door operator systems are available on the market for maintaining a garage door either in a closed or open position. It is clear that the systems should be relatively easy to use and should be able to open the door relatively rapidly to allow quick and easy access to the garage. In addition, many systems are provided which include detectors, pressure detectors and the like that sense when the garage door is being brought down and the bottom edge of the door comes in contact with an obstacle prior to the door reaching the fully closed position. These systems are important because they prevent the garage door from closing on people, pets or small objects and, therefore, prevent personal injury and property damage. One of the drawbacks of such systems, however, is that for some such systems, when the door has been closed, if a lifting force is applied to the door, or instance by an unwanted intruder grabbing the handle of the door and attempting to raise it by jacking the door or the like, some systems through a force measurement routine, automatically cause the door to be opened, in order to prevent what the garage door operator senses might be potential harm. Of course, if the person operating the door is attempting to break and enter the garage for nefarious purposes and it is important that while the system prevents harm, the system also be provided such that the door cannot be forced open if the operator does not want it to be and if no persons or property are in danger.
A system available from the Stanley Company provides a garage door operator having upper travel limit and lower travel limit switches associated therewith. The switches may be set or moved so that the limits of travel may be changed. In the Stanley system, for instance, if the door has reached a nominal closed position and the operator has its down limit switch position changed, the door will actually dynamically track changes in the switch position and open or close according to switch commands.
Mechanical systems may be available that in effect, jam the door closed; however, once these systems are placed in effect, if a person not knowing that the door is down and effectively mechanically locked attempts to open the door the garage door operator then attempts to lift the door against the locking mechanism and the garage door operator may be inadvertently damaged thereby or, at the very least, not open the door because it is locked.
What is needed then is a system which provides a sensing modality for a garage door or other barrier operator which, while maintaining all safety features to prevent personal injury or property damage due to unwanted closing of the door, nevertheless senses when an intruder attempts to open the door and prevents the door from being opened by a positive drive force provided by the garage door operator motor.
The invention relates, in general, to a barrier system operator and, in particular, to a garage door operator which while having all safety features for preventing personal injury and property damage due to inadvertent closing of the garage door, nevertheless provides a positively actuated door closure system which prevents forcing the door once it has closed without having detected any objects underneath it. The system includes a barrier drive including an electric motor which may be connected to a belt, chain or screw drive. Means are provided for detecting motion of the movable barrier. These means may include a motor tachometer, upper and lower limit switches and the like. Means are also provided for detecting when a barrier command signal has been given to the barrier drive so that when a door has been commanded by a radio frequency control, the keypad control, indoor wired control or the like to open, the door may be automatically opened. The system also includes a storage device for storing the commanded state of the barrier drive which may be a microcontroller or a microprocessor in combination with a memory or some other integrated circuit device capable of storing digital or analog information. The commanded state is stored and is then compared in a comparator means with the position indicated by the barrier detection. In the event that the comparison of the barrier state signal and the barrier position signal indicates that the system already has been in a lowered position, usually for given time intervals, such as 27 seconds and attempt is made to raise the door causing unwanted motion of the door when there has been no up command given, an alarm signal is generated which may be passed through electronic and electromechanical logic to the door motor causing the door motor to provide thrust to the door to hold the door in the closed position.
In the alternative, the system may also provide a signal to operate a visual or audio alarm or to call over a telephonic or other wired system to a police department or to a security service to indicate that the system is being broken into.
It is a principal object of the present invention to provide a barrier operator for opening and closing a movable barrier which includes an electronic system for detecting when forced entry is being attempted on the carrier and for preventing the barrier from being opened.
Other objects of this invention will become obvious to one of ordinary skill in the art upon a perusal of the following specification and claims in light of the accompanying drawings.